The invention relates generally to ultrasonic transducer assemblies and, more particularly, to methods of fabricating ultrasonic transducer assemblies.
Ultrasonic transducer assemblies are typically employed in applications including non-destructive evaluation (NDE) and medical diagnostic imaging, such as ultrasound applications and computed tomography (CT). The ultrasonic transducer assembly generally includes an array of ultrasonic transducers coupled to an electronics array. As explained in commonly assigned U.S. Pat. No. 7,892,176, Robert Wodnicki et al. “Monitoring or imaging system with interconnect structure for large area sensor array,” which is incorporated by reference herein in its entirety, transducer arrays in ultrasound probe assemblies typically span an area no larger than about 20 cm2. For new medical applications, such as screening for internal bleeding and tumors, much larger arrays, on the order of 300 cm2, are required. In non-medical applications even larger arrays may be desired.
The ultrasonic transducer array generally includes hundreds or thousands of individual transducers. Piezoelectric transducers (for example, PZT) are a widely used type of ultrasonic transducer. Piezoelectric sensors generally include a piezoelectric material capable of changing physical dimensions when subjected to electrical or mechanical stress. In addition, piezoelectric sensors may include layers of matching materials and damping materials.
Similarly, the electronics array includes hundreds or thousands of integrated interface circuits (or “cells”) which are electrically coupled to provide electrical control of the transducers for beam forming, signal amplification, control functions, signal processing, etc. In particular, each transducer sub-array or chip in the transducer array is typically coupled to an integrated circuit chip to provide individual control of each sensor.
Such large arrays may be formed by tiling of a large number of transducer modules in rows and columns. The array may be one dimensional (1D) (a linear array or row of acoustic elements) for two-dimensional (2D) imaging. Similarly, the array may be a 2D array for volumetric imaging. Each transducer module comprises a subarray of transducer cells and an integrated circuit coupled to the subarray. Fabricating the transducer array and the electronics array, and coupling the two arrays together, provides a number of design challenges. For example, performance of a large area transducer array is significantly degraded when there are significant variations in the spacing between modules.
Further, for many current medium-sized arrays, significant muting challenges exist to bring the connections from the nearby electronics into the sensor array. In addition, these arrays are limited by the available routing density and also by the parasitic capacitances of the traces.
It would therefore be desirable to provide acoustic arrays with controlled spacing between the transducer elements. It would further be desirable to provide acoustic arrays that can be readily assembled into a larger assembly and coupled with front end electronics in an arrangement with low parasitic capacitance. It would also be desirable to provide methods of manufacturing the acoustic arrays and the overall assemblies.